Certified Rhythm Analysis Technician (CRAT) Practice Exam

In sinus arrhythmia, the fundamental characteristic is that there is a consistent relationship between the P waves and the QRS complexes. In a normal sinus rhythm, the electrical impulse originates from the sinoatrial (SA) node, leading to the generation of a P wave that signifies atrial depolarization, followed by the QRS complex indicating ventricular depolarization. Typically, in sinus arrhythmia, there is one P wave for every QRS complex. This indicates that each P wave corresponds to a single heartbeat, representing a normal conduction pathway through the electrical system of the heart, even though the rhythm may be irregular.

The other options highlight varying patterns in conduction that do not apply to sinus arrhythmia. The rhythm does not show a distinct ratio greater than one P wave per QRS complex, nor is there a lack of discernibility in their relationship. Thus, the identification of one P wave per QRS complex is a defining feature of normal conduction in the presence of sinus arrhythmia, making that the correct choice.